ULTRASONIC ALARM DEVICE FOR OBSTACLE

摘要

PURPOSE:To detect deterioration of the performance of a transmitting/receiving means for an obstacle alarm device which radiates an ultrasonic wave and receives its reflected wave to detect a range, by detecting the receiving level that is directly transmitted to a receiving means from a transmitting means. CONSTITUTION:A pulse signal is produced by a timing signal generator 4, and the transmitting operation of a signal transmitter 5 is controlled to drive an ultrasonic wave transmitting element 7. Thus the ultrasonic wave is transmitted into the space. Then a receiving signal that is directly transmitted between the element 7 and an ultrasonic wave receiving element 9 is obtained along with a receiving signal produced from the reflected wave of an obstacle 17. At the same time, a level signal is produced from a threshold level control circuit 8 and a setting circuit 21 at a time point when the pulse is generated from the generator 4. A reflected receiving wave produces an alarm 16 via a comparator 12 in case some obstacle 17 exists within a dangerous range. A direct receiving wave is applied to a comparator 18 and compared with the maintenance comparison level. Then the alarm 16 is produced when a fault arises by detecting waves through a wave detector 19. In such a way, the self-checking is possible for a system by discriminating the deterioration of performance of the ultrasonic wave transmitting/receiving element.